I have not had any problems with security updates for years now. But this one completely hosed my computer. I run Tiger on a G4 so I admit it is old, but after applying the update mail stopped working. Safari and Firefox also refused to open without crashing. Some apps could still reach the internet but not the ones I wanted. I believe many other apps were also not working quite right but I gave up trying to fix this after the usual repairing permissions, trashing preferences etc. failed to do anything. I luckily had a backup of the OS which I restored to a new drive and now I am mostly okay but I will not reinstall this and I would warn anyone with an old G4 to avoid this like the plague.